OLED Pixel Circuit with Shared Reference-Voltage Leakage Control
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Solution Overview
Problem
Existing display devices face issues with current leakage in the electric current flow path, limiting the usable range of reference voltages and affecting the expression of black gradation in organic light-emitting diodes (OLEDs).
Innovation Solution
A display apparatus with a shared circuit that provides a reference voltage and includes transistors operating on different control signals to minimize leakage current and increase the usable range of reference voltages, utilizing a first and second transistor connected in series and a capacitor to stabilize the voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reference voltage is provided to a light-emitting element through a switching transistor, then the pixel circuit can operate with controlled voltage, but current leakage occurs to the light-emitting element which restricts the usable range of reference voltage
Solution Approach 1:
The pixel circuit is divided into multiple independent transistor components (switching transistor, driving transistor, emission control transistor) that can be independently controlled. This segmentation allows the reference voltage to be distributed through controlled paths, reducing unwanted current leakage while maintaining voltage control capability across different operational phases.
Solution Approach 2:
The patent employs dynamic control of transistor states through multiple control signals (first control signal, second control signal, light-emitting signal) that change over time. The switching transistor and other transistors are dynamically switched between on and off states to control current flow paths, enabling the reference voltage to be adjusted within a broader range without causing harmful leakage currents.
2Illumination intensity
If the usable range of reference voltage is increased to improve black gradation expression, then current leakage to the light-emitting element increases
Solution Approach 1:
The pixel circuit incorporates feedback mechanisms through the driving transistor and emission control transistor that monitor and adjust the current flow to the light-emitting element. This feedback control allows the system to maintain precise control over the actual current reaching the light-emitting element, enabling broader reference voltage ranges to be used for improved black gradation expression without causing harmful leakage currents.
Solution Approach 2:
The driving transistor and emission control transistor act as intermediary components between the reference voltage source and the light-emitting element. These intermediary transistors provide controlled current paths that allow the reference voltage to be adjusted for better black gradation expression while preventing direct harmful current leakage to the light-emitting element through regulated conduction paths.
Data Source
AI summary
A display apparatus includes a mode controller configured to generate a first control signal and a second control signal, a gate drive circuit configured to generate a light-emitting signal, a first scan signal, and a second scan signal, a shared circuit connected to a reference voltage line configured to provide a reference voltage, the shared circuit comprising a first transistor configured to operate based on the first scan signal, and a second transistor connected to the first transistor in series and configured to operate based on the second scan signal and a first pixel circuit connected to the mode controller and the gate drive circuit, wherein the first pixel circuit includes a driving transistor, a third transistor configured to operate based on the light-emitting signal and connected to the second transistor, a fourth-first transistor configured to operate based on the first control signal, a fourth-second transistor configured to operate based on the second control signal, a first light-emitting element connected to the fourth-first transistor, a second light-emitting element connected to the fourth-second transistor and a capacitor connected to the first transistor, the second transistor, the third transistor, and the driving transistor.